The present invention relates generally to pressure responsive valve assemblies and more particularly to such valve assemblies adapted for use in reciprocating piston type compressors, such as refrigeration compressors.
Reciprocating piston type compressors typically employ suction and discharge pressure actuated valving mounted at the end of the cylinder between the head and cylinder housing. In designing these valve assemblies it is of critical importance to overall system operation to provide a sufficiently large port area to permit the flow of a maximum volume of fluid within a given time period and at an acceptably small pressure drop. This is particularly true for refrigeration compressors employed in air conditioning systems because of the relatively high mass flow rates generally required in such systems.
Associated and conflicting with the desirability to maximize port area for a given size cylinder is the need to reduce the weight of the moving valve member so as to limit the inertia effect thereof. Noise of operation should also be minimized. These aspects take on increasing importance with high speed compressors.
Another important design objective is to minimize the reexpansion or clearance volume of the cylinder. The valving and cylinder top end wall should have a shape complementary with that of the top of the piston and as flat as possible to enable the piston to reduce the volume of the compression chamber to an absolute minimum during the compression stroke without restricting gas flow. While it may be possible to accomplish this objective by design of complex piston head shapes, manufacturing thereof becomes expensive, assembly more difficult, and throttling losses generally occur as the piston approaches top dead center. Reduction of reexpansion volume is of great importance in refrigeration compressors having relatively low mass flow rates, such as those units employed in very low temperature refrigeration systems, as well as in units for heat pump applications.
It is therefore the primary object of this invention to provide an improved valve and an improved valve and seat combination for use as a discharge valve in a reciprocating gas compressor, such as, for example, the compressors used in refrigeration equipment, which valve and valve-seat combination improves the efficiency of the compressor and is characterized by its improved flow characteristics at all valve lifts, good sealing without permanent deformation of the valve, long life, quietness in operation and its ability to operate in high speed compressors.
The present invention provides an improved valve assembly utilizing a valve member the entire area of which is subjected to valve actuating pressure differentials and which is fabricated in a light-weight manner so that high force to weight ratios are obtained for a given port size. This maximizes acceleration and hence efficiency, especially at high speeds. Further, the design of the valve member and associated valve plate is such as to present a substantially flat, flush end wall for the compression chamber. Thus, the reexpansion volume for the compression chamber is substantially reduced over conventional valving arrangements and simple flat topped pistons (or pistons with a minimum of top surface contour) can be used. Also, because of the lightweight characteristics of the valve member, valving action is faster and port size may be increased without detrimental inertial effects. The use of a polymeric material for the valve member in the preferred embodiment and the relative geometries of the valve member and valve seat also reduce valve noise generated by the recurring impact of the valve member and valve seat. With the present invention valve port area is not a function of reexpansion volume; each can be optimized independently. Therefore, the valve assembly of the present invention is ideally suited for use both in air conditioning applications as well as heat pumps and low temperature units. Further, the present arrangement can be used to maximize the use of the cylinder head area for valving.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.